IPA: /ˌɪn.sɪˈkjʊr/
KK: /ɪnˈsɪkjʊr/
Not feeling confident or safe; having doubts about oneself or one's situation.
She felt insecure about her performance in the competition.
Insecure → It is formed from "in-" (meaning not) and "securus" (from Latin, meaning safe or secure). The word "insecure" means not safe or lacking security.
Think of 'not' ('in-') being added to 'safe' ('securus') — that's why insecure means not safe.